High speed and high integration of LSIs and enhanced memory capacity have been advanced in recent years. This consequently leads to rapid advance in miniaturization, lightweighting and thinning of various electronic components. Heretofore, wiring boards and the like used in the field of these electronic components employ, as an insulating material, a cyclic olefin copolymer such as those described in Patent Document 1. The insulating material has been used in a copper-clad substrate including a copper foil joined to a surface thereof, and a wiring board for high frequency applications.